Hydrogenated Polydecene

This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition

Issued and maintained by the United States Pharmacopeial Convention (USP)

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C_30≤n≤70H_2n+2

1-Decene, homopolymer, hydrogenated

CAS RN: 68037-01-4.

1 DEFINITION

Hydrogenated Polydecene is a mixture of saturated, synthetic hydrocarbons in the range C₃₀H₆₂ through C₇₀H₁₄₂ made from direct oligomerization of 1-decene (C alpha olefin). The oligomer mixture may be distilled to fractions of a suitable calculated viscosity and hydrogenated to reach saturation, or it may be hydrogenated to reach saturation and then distilled to the desired viscosity. The requirements for specific gravity, viscosity, and content of decene oligomer differ for the various types of Hydrogenated Polydecene, as set forth in the two tables below. Hydrogenated Polydecene may contain a suitable stabilizer.

Specific Gravity and Viscosity

Content of Decene Oligomers

2 IDENTIFICATION

A. The chromatogram of the Sample solution from the test for Content of Decene Oligomer exhibits major peaks for trimers, tetramers, pentamers, hexamers, and possibly heptamers. The decene oligomer content is within the range given in the table Content of Decene Oligomers in the Definition for the labeled type of Hydrogenated Polydecene.

3 ASSAY

Content of Decene Oligomer

System suitability solution: 10 mg/mL of hexadecane, 10 mg/mL of squalane, and 1 mg/mL of tetradecane in pentane

Sample solution: Dissolve 0.1 mL of Hydrogenated Polydecene in 10 mL of pentane.

Chromatographic system

(See Chromatography 〈621〉, System Suitability.)

Mode: GC

Detector: Flame ionization

Column: 0.52-mm × 16-m fused-silica capillary; coated with 0.1-mm stationary phase G2

Carrier gas: Helium

Flow rate: 10 mL/min

Injection volume: 2 μL

Temperatures

Injection port: 310°

Detector: 320°

Column: See Table 1.

Table 1

System suitability

Sample: System suitability solution

[Note—The retention time for squalane is about 18 min; the relative retention times for tetradecane, hexadecane, and squalane are about 0.5, 0.6, and 1.0, respectively.]

Suitability requirements

Resolution: NLT 2.0 between tetradecane and hexadecane

Relative standard deviation: NMT 2.0% for each peak

Analysis

Sample: Sample solution

Record the chromatogram, and measure the areas for the major peaks.

[Note—The tetramer oligomer has a retention time of about 23 min. The trimer, pentamer, hexamer, and heptamer oligomers, if present, have relative retention times of about 0.8, 1.1, 1.3, and 1.4, respectively, relative to the tetramer.]

Calculate the percentage of each oligomer present:

Result = (r_U/r_T) × 100

r_U = response of each oligomer

r_T = sum of the responses of all the peaks, excluding the solvent peak

Acceptance criteria: The decene oligomer content is within the limits specified in the table Content of Decene Oligomers in the Definition.

4 IMPURITIES

Limit of Nickel

Nickel stock solution: Immediately before use, dilute an appropriate quantity of organometallic standard¹ with kerosene to prepare a solution containing the equivalent of 1.0 μg/mL of nickel.

Standard solutions: Transfer 0.5, 1.0, 2.0, and 4.0 mL of Nickel stock solution, respectively, to four identical 10-mL volumetric flasks, dilute the contents of each flask with kerosene to volume, and mix. These Standard solutions contain, respectively, 0.05, 0.1, 0.2, and 0.40 μg/mL of nickel. [Note—The calibration range, especially the upper limit, can be adjusted for certain instruments, provided that instrument validation and calibration linearity are achieived.]

Sample solution: 0.3 g/mL of Hydrogenated Polydecene in kerosene. [Note—If necessary, dilute with an appropriate quantity of kerosene to obtain a reading within the calibrated absorbance range.]

Instrumental conditions

(See Atomic Absorption Spectroscopy 〈852〉.)

Mode: Graphite furnace atomic absorption spectrophotometer equipped with a deuterium background corrector and a pyrolytically coated tube with platform

Analytical wavelength: 232.0 nm (nickel emission line)

Injection volume: 20 μL

Lamp: Nickel hollow-cathode

Blank: Kerosene

Temperature: See Table 2.

[Note—The temperature program may be modified to obtain optimum furnace temperatures.]

Table 2

Analysis

Samples: Standard solutions and Sample solution

Place the Standard solutions and the Sample solution in an oven, setting the temperature at about 60° during the period of determination, and shake these solutions vigorously before analysis. Use micropipettor and pipettor tips to make all injections. [Note—Positive displacement pipets can be used when viscosity may become a problem.]

Pretreat the pipettor tip by pipetting and then discarding 20 μL of heptane. The tip must be pretreated before each injection. [Note—The film of heptane remaining on the wall of the tip facilitates a reproducible transfer of the oil sample.]

Separately inject the Standard solutions and the Sample solution into a graphite furnace, and concomitantly determine the integrated absorbances of the Standard solutions and the Sample solution.

Plot the integrated absorbances of the Standard solutions versus concentration, in μg/mL, of nickel, and draw the straight line best fitting the four plotted points. From the graph so obtained, determine the concentration of nickel, C, in μg/mL, in the Sample solution.

Calculate the content of nickel in the Hydrogenated Polydecene taken:

Result = C/C_U

C = concentration of nickel obtained from the graph (μg/mL)

C_U = concentration of nickel in the Sample solution (g/mL)

Acceptance criteria: NMT 1 μg/g

Limit of Short-Chain Hydrocarbons

System suitability solution, Sample solution, Chromatographic system, System suitability, and Analysis: Proceed as directed in the test for Content of Decene Oligomer.

Calculate the percentage of each of the short-chain hydrocarbons present:

Result = (r_U/r_T) × 100

r_U = peak response of any peak eluting before the trimer but different from the solvent peak

r_T = sum of the responses of all the peaks in the chromatogram, excluding the solvent peak

Acceptance criteria: NMT 2.5% of total short-chain hydrocarbons is found.

5 SPECIFIC TESTS

Specific Gravity 〈841〉

Analysis: Determine at 20°.

Acceptance criteria: Meets the requirements of the specific gravity range specified in the table Specific Gravity and Viscosity in the Definition for the labeled type

Viscosity—Capillary Methods 〈911〉

Analysis: Determine using a capillary viscometer, in a liquid bath maintained at 40.0 ± 0.1°.

Acceptance criteria: Meets the requirements of the viscosity range specified in the table Specific Gravity and Viscosity in the Definition for the labeled type.

Readily Carbonizable Substances Test 〈271〉

Standard solution: 3 mL of ferric chloride CS, 1.5 mL of cobaltous chloride CS, and 0.5 mL of cupric sulfate CS in a glass-stoppered test tube previously treated to remove organic matter (see Cleaning Glass Apparatus 〈1051〉).

Sample: 5 mL

Analysis: Transfer the Sample to a glass-stoppered test tube previously treated to remove organic matter (see Cleaning Glass Apparatus〈1051〉), add 5 mL of sulfuric acid, and heat in a boiling water bath for 30 s. Quickly remove the test tube, and, while holding the stopper in place, shake three times in a vertically reciprocating cycle with an amplitude of about 13 cm. Repeat this procedure every 30 s for 10 min.

Do not keep the test tube out of the water bath any longer than 3 s for each shaking cycle. Remove the test tube from the water bath, and let it cool for about 20 min to room temperature.

Acceptance criteria: The oil phase of the Sample may turn hazy but remains colorless; the interface between the two layers is free from solids; and the acid layer does not become darker than the standard color produced by the Standard solution, the Standard solution being overlaid with 5 mL of Hydrogenated Polydecene.

6 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in tight containers. No storage requirements are specified.

Labeling: Label it to indicate, as part of the official title, the Hydrogenated Polydecene type (Type I, Type II, or Type III), and label it to indicate the name and concentration of any added stabilizer.

¹ Suitable organometallic standards are available from, e.g., Continental Oil Co., Ponca City, OK (Conostan, 100 ppm), or Merck, D-6100 Darmstadt, Germany (metal in standard oil, 1000 ppm).